Editor's Summary

2 July 2009

A limit on CO₂ drawdown

Despite the occurrence of high rates of global silicate rock weathering likely to increase the drawdown of atmospheric CO₂ — and hence temperatures — CO₂ concentrations are thought to have stayed above about 180 parts per million throughout the past 24 million years (compared to about 385 p.p.m. today, and a 'pre-industrial' 280 p.p.m.). Based on terrestrial and geochemical carbon-cycle modelling simulations, Pagani et al. suggest that it may have been the actions of land plants that strongly attenuated long-term CO₂ variability and helped prevent the onset of icehouse conditions. As CO₂ falls to critically low levels due to increased chemical weathering, they find that vegetation activity is substantially reduced, compromising the capacity to further enhance silicate chemical weathering.

News and Views: Biogeochemistry: Climatic plant power

Levels of atmospheric carbon dioxide constrain vegetation types and thus also non-biological uptake during rock weathering. That's the reasoning used to explain why CO₂ levels did not fall below a certain point in the Miocene.

Yves Goddéris & Yannick Donnadieu

doi:10.1038/460040a

Full Text | PDF (985K)

Letter: The role of terrestrial plants in limiting atmospheric CO₂ decline over the past 24 million years

Mark Pagani, Ken Caldeira, Robert Berner & David J. Beerling

doi:10.1038/nature08133

First paragraph | Full Text | PDF (874K) | Supplementary information